| /* SPDX-License-Identifier: LGPL-2.1-or-later */ |
| |
| #include <errno.h> |
| #include <fcntl.h> |
| #include <sys/mount.h> |
| |
| #include "alloc-util.h" |
| #include "fd-util.h" |
| #include "fileio.h" |
| #include "fs-util.h" |
| #include "missing_stat.h" |
| #include "missing_syscall.h" |
| #include "mkdir.h" |
| #include "mountpoint-util.h" |
| #include "parse-util.h" |
| #include "path-util.h" |
| #include "stat-util.h" |
| #include "stdio-util.h" |
| #include "strv.h" |
| #include "user-util.h" |
| |
| /* This is the original MAX_HANDLE_SZ definition from the kernel, when the API was introduced. We use that in place of |
| * any more currently defined value to future-proof things: if the size is increased in the API headers, and our code |
| * is recompiled then it would cease working on old kernels, as those refuse any sizes larger than this value with |
| * EINVAL right-away. Hence, let's disconnect ourselves from any such API changes, and stick to the original definition |
| * from when it was introduced. We use it as a start value only anyway (see below), and hence should be able to deal |
| * with large file handles anyway. */ |
| #define ORIGINAL_MAX_HANDLE_SZ 128 |
| |
| int name_to_handle_at_loop( |
| int fd, |
| const char *path, |
| struct file_handle **ret_handle, |
| int *ret_mnt_id, |
| int flags) { |
| |
| _cleanup_free_ struct file_handle *h = NULL; |
| size_t n = ORIGINAL_MAX_HANDLE_SZ; |
| |
| assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0); |
| |
| /* We need to invoke name_to_handle_at() in a loop, given that it might return EOVERFLOW when the specified |
| * buffer is too small. Note that in contrast to what the docs might suggest, MAX_HANDLE_SZ is only good as a |
| * start value, it is not an upper bound on the buffer size required. |
| * |
| * This improves on raw name_to_handle_at() also in one other regard: ret_handle and ret_mnt_id can be passed |
| * as NULL if there's no interest in either. */ |
| |
| for (;;) { |
| int mnt_id = -1; |
| |
| h = malloc0(offsetof(struct file_handle, f_handle) + n); |
| if (!h) |
| return -ENOMEM; |
| |
| h->handle_bytes = n; |
| |
| if (name_to_handle_at(fd, path, h, &mnt_id, flags) >= 0) { |
| |
| if (ret_handle) |
| *ret_handle = TAKE_PTR(h); |
| |
| if (ret_mnt_id) |
| *ret_mnt_id = mnt_id; |
| |
| return 0; |
| } |
| if (errno != EOVERFLOW) |
| return -errno; |
| |
| if (!ret_handle && ret_mnt_id && mnt_id >= 0) { |
| |
| /* As it appears, name_to_handle_at() fills in mnt_id even when it returns EOVERFLOW when the |
| * buffer is too small, but that's undocumented. Hence, let's make use of this if it appears to |
| * be filled in, and the caller was interested in only the mount ID an nothing else. */ |
| |
| *ret_mnt_id = mnt_id; |
| return 0; |
| } |
| |
| /* If name_to_handle_at() didn't increase the byte size, then this EOVERFLOW is caused by something |
| * else (apparently EOVERFLOW is returned for untriggered nfs4 mounts sometimes), not by the too small |
| * buffer. In that case propagate EOVERFLOW */ |
| if (h->handle_bytes <= n) |
| return -EOVERFLOW; |
| |
| /* The buffer was too small. Size the new buffer by what name_to_handle_at() returned. */ |
| n = h->handle_bytes; |
| if (offsetof(struct file_handle, f_handle) + n < n) /* check for addition overflow */ |
| return -EOVERFLOW; |
| |
| h = mfree(h); |
| } |
| } |
| |
| static int fd_fdinfo_mnt_id(int fd, const char *filename, int flags, int *ret_mnt_id) { |
| char path[STRLEN("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)]; |
| _cleanup_free_ char *fdinfo = NULL; |
| _cleanup_close_ int subfd = -1; |
| char *p; |
| int r; |
| |
| assert(ret_mnt_id); |
| assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0); |
| |
| if ((flags & AT_EMPTY_PATH) && isempty(filename)) |
| xsprintf(path, "/proc/self/fdinfo/%i", fd); |
| else { |
| subfd = openat(fd, filename, O_CLOEXEC|O_PATH|(flags & AT_SYMLINK_FOLLOW ? 0 : O_NOFOLLOW)); |
| if (subfd < 0) |
| return -errno; |
| |
| xsprintf(path, "/proc/self/fdinfo/%i", subfd); |
| } |
| |
| r = read_full_virtual_file(path, &fdinfo, NULL); |
| if (r == -ENOENT) /* The fdinfo directory is a relatively new addition */ |
| return -EOPNOTSUPP; |
| if (r < 0) |
| return r; |
| |
| p = startswith(fdinfo, "mnt_id:"); |
| if (!p) { |
| p = strstr(fdinfo, "\nmnt_id:"); |
| if (!p) /* The mnt_id field is a relatively new addition */ |
| return -EOPNOTSUPP; |
| |
| p += 8; |
| } |
| |
| p += strspn(p, WHITESPACE); |
| p[strcspn(p, WHITESPACE)] = 0; |
| |
| return safe_atoi(p, ret_mnt_id); |
| } |
| |
| static bool filename_possibly_with_slash_suffix(const char *s) { |
| const char *slash, *copied; |
| |
| /* Checks whether the specified string is either file name, or a filename with a suffix of |
| * slashes. But nothing else. |
| * |
| * this is OK: foo, bar, foo/, bar/, foo//, bar/// |
| * this is not OK: "", "/", "/foo", "foo/bar", ".", ".." … */ |
| |
| slash = strchr(s, '/'); |
| if (!slash) |
| return filename_is_valid(s); |
| |
| if (slash - s > PATH_MAX) /* We want to allocate on the stack below, hence do a size check first */ |
| return false; |
| |
| if (slash[strspn(slash, "/")] != 0) /* Check that the suffix consist only of one or more slashes */ |
| return false; |
| |
| copied = strndupa(s, slash - s); |
| return filename_is_valid(copied); |
| } |
| |
| static bool is_name_to_handle_at_fatal_error(int err) { |
| /* name_to_handle_at() can return "acceptable" errors that are due to the context. For |
| * example the kernel does not support name_to_handle_at() at all (ENOSYS), or the syscall |
| * was blocked (EACCES/EPERM; maybe through seccomp, because we are running inside of a |
| * container), or the mount point is not triggered yet (EOVERFLOW, think nfs4), or some |
| * general name_to_handle_at() flakiness (EINVAL). However other errors are not supposed to |
| * happen and therefore are considered fatal ones. */ |
| |
| assert(err < 0); |
| |
| return !IN_SET(err, -EOPNOTSUPP, -ENOSYS, -EACCES, -EPERM, -EOVERFLOW, -EINVAL); |
| } |
| |
| int fd_is_mount_point(int fd, const char *filename, int flags) { |
| _cleanup_free_ struct file_handle *h = NULL, *h_parent = NULL; |
| int mount_id = -1, mount_id_parent = -1; |
| bool nosupp = false, check_st_dev = true; |
| STRUCT_STATX_DEFINE(sx); |
| struct stat a, b; |
| int r; |
| |
| assert(fd >= 0); |
| assert(filename); |
| assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0); |
| |
| /* Insist that the specified filename is actually a filename, and not a path, i.e. some inode further |
| * up or down the tree then immediately below the specified directory fd. */ |
| if (!filename_possibly_with_slash_suffix(filename)) |
| return -EINVAL; |
| |
| /* First we will try statx()' STATX_ATTR_MOUNT_ROOT attribute, which is our ideal API, available |
| * since kernel 5.8. |
| * |
| * If that fails, our second try is the name_to_handle_at() syscall, which tells us the mount id and |
| * an opaque file "handle". It is not supported everywhere though (kernel compile-time option, not |
| * all file systems are hooked up). If it works the mount id is usually good enough to tell us |
| * whether something is a mount point. |
| * |
| * If that didn't work we will try to read the mount id from /proc/self/fdinfo/<fd>. This is almost |
| * as good as name_to_handle_at(), however, does not return the opaque file handle. The opaque file |
| * handle is pretty useful to detect the root directory, which we should always consider a mount |
| * point. Hence we use this only as fallback. Exporting the mnt_id in fdinfo is a pretty recent |
| * kernel addition. |
| * |
| * As last fallback we do traditional fstat() based st_dev comparisons. This is how things were |
| * traditionally done, but unionfs breaks this since it exposes file systems with a variety of st_dev |
| * reported. Also, btrfs subvolumes have different st_dev, even though they aren't real mounts of |
| * their own. */ |
| |
| if (statx(fd, filename, (FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : AT_SYMLINK_NOFOLLOW) | |
| (flags & AT_EMPTY_PATH) | |
| AT_NO_AUTOMOUNT, STATX_TYPE, &sx) < 0) { |
| if (!ERRNO_IS_NOT_SUPPORTED(errno) && !ERRNO_IS_PRIVILEGE(errno)) |
| return -errno; |
| |
| /* If statx() is not available or forbidden, fall back to name_to_handle_at() below */ |
| } else if (FLAGS_SET(sx.stx_attributes_mask, STATX_ATTR_MOUNT_ROOT)) /* yay! */ |
| return FLAGS_SET(sx.stx_attributes, STATX_ATTR_MOUNT_ROOT); |
| else if (FLAGS_SET(sx.stx_mask, STATX_TYPE) && S_ISLNK(sx.stx_mode)) |
| return false; /* symlinks are never mount points */ |
| |
| r = name_to_handle_at_loop(fd, filename, &h, &mount_id, flags); |
| if (r < 0) { |
| if (is_name_to_handle_at_fatal_error(r)) |
| return r; |
| if (r != -EOPNOTSUPP) |
| goto fallback_fdinfo; |
| |
| /* This kernel or file system does not support name_to_handle_at(), hence let's see |
| * if the upper fs supports it (in which case it is a mount point), otherwise fall |
| * back to the traditional stat() logic */ |
| nosupp = true; |
| } |
| |
| r = name_to_handle_at_loop(fd, "", &h_parent, &mount_id_parent, AT_EMPTY_PATH); |
| if (r < 0) { |
| if (is_name_to_handle_at_fatal_error(r)) |
| return r; |
| if (r != -EOPNOTSUPP) |
| goto fallback_fdinfo; |
| if (nosupp) |
| /* Both the parent and the directory can't do name_to_handle_at() */ |
| goto fallback_fdinfo; |
| |
| /* The parent can't do name_to_handle_at() but the directory we are |
| * interested in can? If so, it must be a mount point. */ |
| return 1; |
| } |
| |
| /* The parent can do name_to_handle_at() but the directory we are interested in can't? If |
| * so, it must be a mount point. */ |
| if (nosupp) |
| return 1; |
| |
| /* If the file handle for the directory we are interested in and its parent are identical, |
| * we assume this is the root directory, which is a mount point. */ |
| |
| if (h->handle_bytes == h_parent->handle_bytes && |
| h->handle_type == h_parent->handle_type && |
| memcmp(h->f_handle, h_parent->f_handle, h->handle_bytes) == 0) |
| return 1; |
| |
| return mount_id != mount_id_parent; |
| |
| fallback_fdinfo: |
| r = fd_fdinfo_mnt_id(fd, filename, flags, &mount_id); |
| if (IN_SET(r, -EOPNOTSUPP, -EACCES, -EPERM)) |
| goto fallback_fstat; |
| if (r < 0) |
| return r; |
| |
| r = fd_fdinfo_mnt_id(fd, "", AT_EMPTY_PATH, &mount_id_parent); |
| if (r < 0) |
| return r; |
| |
| if (mount_id != mount_id_parent) |
| return 1; |
| |
| /* Hmm, so, the mount ids are the same. This leaves one special case though for the root file |
| * system. For that, let's see if the parent directory has the same inode as we are interested |
| * in. Hence, let's also do fstat() checks now, too, but avoid the st_dev comparisons, since they |
| * aren't that useful on unionfs mounts. */ |
| check_st_dev = false; |
| |
| fallback_fstat: |
| /* yay for fstatat() taking a different set of flags than the other _at() above */ |
| if (flags & AT_SYMLINK_FOLLOW) |
| flags &= ~AT_SYMLINK_FOLLOW; |
| else |
| flags |= AT_SYMLINK_NOFOLLOW; |
| if (fstatat(fd, filename, &a, flags) < 0) |
| return -errno; |
| if (S_ISLNK(a.st_mode)) /* Symlinks are never mount points */ |
| return false; |
| |
| if (fstatat(fd, "", &b, AT_EMPTY_PATH) < 0) |
| return -errno; |
| |
| /* A directory with same device and inode as its parent? Must |
| * be the root directory */ |
| if (a.st_dev == b.st_dev && |
| a.st_ino == b.st_ino) |
| return 1; |
| |
| return check_st_dev && (a.st_dev != b.st_dev); |
| } |
| |
| /* flags can be AT_SYMLINK_FOLLOW or 0 */ |
| int path_is_mount_point(const char *t, const char *root, int flags) { |
| _cleanup_free_ char *canonical = NULL; |
| _cleanup_close_ int fd = -1; |
| int r; |
| |
| assert(t); |
| assert((flags & ~AT_SYMLINK_FOLLOW) == 0); |
| |
| if (path_equal(t, "/")) |
| return 1; |
| |
| /* we need to resolve symlinks manually, we can't just rely on |
| * fd_is_mount_point() to do that for us; if we have a structure like |
| * /bin -> /usr/bin/ and /usr is a mount point, then the parent that we |
| * look at needs to be /usr, not /. */ |
| if (flags & AT_SYMLINK_FOLLOW) { |
| r = chase_symlinks(t, root, CHASE_TRAIL_SLASH, &canonical, NULL); |
| if (r < 0) |
| return r; |
| |
| t = canonical; |
| } |
| |
| fd = open_parent(t, O_PATH|O_CLOEXEC, 0); |
| if (fd < 0) |
| return fd; |
| |
| return fd_is_mount_point(fd, last_path_component(t), flags); |
| } |
| |
| int path_get_mnt_id(const char *path, int *ret) { |
| STRUCT_NEW_STATX_DEFINE(buf); |
| int r; |
| |
| if (statx(AT_FDCWD, path, AT_SYMLINK_NOFOLLOW|AT_NO_AUTOMOUNT, STATX_MNT_ID, &buf.sx) < 0) { |
| if (!ERRNO_IS_NOT_SUPPORTED(errno) && !ERRNO_IS_PRIVILEGE(errno)) |
| return -errno; |
| |
| /* Fall back to name_to_handle_at() and then fdinfo if statx is not supported or we lack |
| * privileges */ |
| |
| } else if (FLAGS_SET(buf.nsx.stx_mask, STATX_MNT_ID)) { |
| *ret = buf.nsx.stx_mnt_id; |
| return 0; |
| } |
| |
| r = name_to_handle_at_loop(AT_FDCWD, path, NULL, ret, 0); |
| if (r == 0 || is_name_to_handle_at_fatal_error(r)) |
| return r; |
| |
| return fd_fdinfo_mnt_id(AT_FDCWD, path, 0, ret); |
| } |
| |
| bool fstype_is_network(const char *fstype) { |
| const char *x; |
| |
| x = startswith(fstype, "fuse."); |
| if (x) |
| fstype = x; |
| |
| return STR_IN_SET(fstype, |
| "afs", |
| "ceph", |
| "cifs", |
| "smb3", |
| "smbfs", |
| "sshfs", |
| "ncpfs", |
| "ncp", |
| "nfs", |
| "nfs4", |
| "gfs", |
| "gfs2", |
| "glusterfs", |
| "pvfs2", /* OrangeFS */ |
| "ocfs2", |
| "lustre", |
| "davfs"); |
| } |
| |
| bool fstype_is_api_vfs(const char *fstype) { |
| return STR_IN_SET(fstype, |
| "autofs", |
| "bpf", |
| "cgroup", |
| "cgroup2", |
| "configfs", |
| "cpuset", |
| "debugfs", |
| "devpts", |
| "devtmpfs", |
| "efivarfs", |
| "fusectl", |
| "hugetlbfs", |
| "mqueue", |
| "proc", |
| "pstore", |
| "ramfs", |
| "securityfs", |
| "sysfs", |
| "tmpfs", |
| "tracefs"); |
| } |
| |
| bool fstype_is_blockdev_backed(const char *fstype) { |
| const char *x; |
| |
| x = startswith(fstype, "fuse."); |
| if (x) |
| fstype = x; |
| |
| return !streq(fstype, "9p") && !fstype_is_network(fstype) && !fstype_is_api_vfs(fstype); |
| } |
| |
| bool fstype_is_ro(const char *fstype) { |
| /* All Linux file systems that are necessarily read-only */ |
| return STR_IN_SET(fstype, |
| "DM_verity_hash", |
| "iso9660", |
| "erofs", |
| "squashfs"); |
| } |
| |
| bool fstype_can_discard(const char *fstype) { |
| return STR_IN_SET(fstype, |
| "btrfs", |
| "ext4", |
| "vfat", |
| "xfs"); |
| } |
| |
| bool fstype_can_uid_gid(const char *fstype) { |
| |
| /* All file systems that have a uid=/gid= mount option that fixates the owners of all files and directories, |
| * current and future. */ |
| |
| return STR_IN_SET(fstype, |
| "adfs", |
| "exfat", |
| "fat", |
| "hfs", |
| "hpfs", |
| "iso9660", |
| "msdos", |
| "ntfs", |
| "vfat"); |
| } |
| |
| int dev_is_devtmpfs(void) { |
| _cleanup_fclose_ FILE *proc_self_mountinfo = NULL; |
| int mount_id, r; |
| char *e; |
| |
| r = path_get_mnt_id("/dev", &mount_id); |
| if (r < 0) |
| return r; |
| |
| r = fopen_unlocked("/proc/self/mountinfo", "re", &proc_self_mountinfo); |
| if (r < 0) |
| return r; |
| |
| for (;;) { |
| _cleanup_free_ char *line = NULL; |
| int mid; |
| |
| r = read_line(proc_self_mountinfo, LONG_LINE_MAX, &line); |
| if (r < 0) |
| return r; |
| if (r == 0) |
| break; |
| |
| if (sscanf(line, "%i", &mid) != 1) |
| continue; |
| |
| if (mid != mount_id) |
| continue; |
| |
| e = strstr(line, " - "); |
| if (!e) |
| continue; |
| |
| /* accept any name that starts with the currently expected type */ |
| if (startswith(e + 3, "devtmpfs")) |
| return true; |
| } |
| |
| return false; |
| } |
| |
| const char *mount_propagation_flags_to_string(unsigned long flags) { |
| |
| switch (flags & (MS_SHARED|MS_SLAVE|MS_PRIVATE)) { |
| case 0: |
| return ""; |
| case MS_SHARED: |
| return "shared"; |
| case MS_SLAVE: |
| return "slave"; |
| case MS_PRIVATE: |
| return "private"; |
| } |
| |
| return NULL; |
| } |
| |
| int mount_propagation_flags_from_string(const char *name, unsigned long *ret) { |
| |
| if (isempty(name)) |
| *ret = 0; |
| else if (streq(name, "shared")) |
| *ret = MS_SHARED; |
| else if (streq(name, "slave")) |
| *ret = MS_SLAVE; |
| else if (streq(name, "private")) |
| *ret = MS_PRIVATE; |
| else |
| return -EINVAL; |
| return 0; |
| } |
